Factors Influencing Retinal Image Contrast -Reykjavik Eye Study

Abstract

Purpose: : We studied factors influencing retinal image contrast of Icelandic adults with transparent lenses by examining backward light scattering and higher order aberration (HOA).

Methods: : Subjects comprised 98 right eyes with a transparent crystalline lens of 98 patients (mean age: 65.5±3.3) out of 573 participants of Reykjavik Eye Study in 2008. A point spread function analyzer (PSF-1000, TOPCON) was used to measure retinal image contrast under condition of best corrected refractive error with mydriasis, through Landolt ring simulation with 3mm entrance pupils. We used scheimpflug slit images photographed by anterior segment analysis system (EAS-1000, NIDEK) to estimate backward light scattering intensity (LSI) and optical distance (mm) of each layer of lens (anterior capsule (A), anterior adult nucleus (B) and central clear zone (C)), then calculated Lens transparent property (LTP), an index of lens transparency (Sasaki H, et al: Ophthalmic Res. 1999). LTP was gained by the formula LTP=LSI at A + LSI at B × optical distance between A and B + LSI at C × optical distance between A and C. Wave Front Analyzer (9000PW, TOPCON) was also used to measure ocular total HOA (µm) with 4mm pupils.

Results: : There was positive correlation between age and LTP (r²=0.317, P<0.001), however, no significant correlation between age and ocular total HOA (r²=0.025, P=0.121). The retinal image contrast degenerated with aging (r²=0.046, P=0.034). There was a significant negative correlation between total HOA and retinal image contrast (r²=0.055 p= 0.020). Meanwhile, there was no remarkable correlation between LTP and retinal image contrast (r²= 0.0002 p=0.897).

Conclusions: : Retinal image contrast of transparent lenses of >60 yrs old subjects decreased along with increase of total higher order aberration. Still, effect of lens transparency was hardly indicated.

Keywords: contrast sensitivity • aging • retina